The long-term goal of this research is to test the hypothesis that the generation of acid in the body resulting from the consumption of exessive amounts of dietary protein leads to the loss of calcium-containing buffers from the skeleton which, over several years, contributes to decreased bone mass, osteoporosis, or other forms of bone disease. We hope to explore, through the following experiments, the relationship between dietary protein, acid formation in the body, urinary calcium and bone loss in an ethnically-diverse population of paremenopausal women. We also plan to investigate whether or not orally-administered buffers can reverse the calcium-wasting effect of excess protein in the same subject population. Taken together, these experiments and studies could constitute a significant first step in our efforts to understand one of the possible mechanisms underlying the development of osteoporosis. Continuing Review of the project referenced reveals that 40 human subjects (0 males, 40 females) have been enrolled to date. The investigators report that as regards the consumption of dietary protein, the study's main focus, urinary calcium excretion has decreased by 55-81% as women switched from their ad lib diets to the Week One diet which contains 0.8g/kg bodyweight. Net renal acid excretion likewise decreases by 25-65% at the same time. This result suggests that decreasing dietary protein can result in a decreased net renal acid production and a consequent urine calcium excretion as per the original hypothesis. Further analysis of the data will not be possible until the investigators are unblinded after the conclusion of data collection. No subjects withdrew from the study. The number of subjects enrolled is equal to the number of subjects approved. The investigators will submit an amendment to increase the number of enrollement.